Wood Burning Basics

Burn Only Dry, Seasoned
Firewood

Freshly cut wood contains up to 80% moisture, and
must be "seasoned" (dried to 20-25% moisture content) before burning.
Wood containing more than 25% moisture is "wet" or "green", and should
never be burned in a fireplace or woodstove. If exposed to rain, a
fallen tree will wet-rot before it ever dries enough to be used for
fuel. To properly season firewood, cut it into stove-sized pieces and
stack it so air can circulate and carry away the moisture as it
evaporates through both ends of each piece. The woodpile must be
sheltered to prevent rainwater from being re-absorbed, which reverses
the drying process: firewood that is exposed to rain will rapidly become
just as wet as it was when freshly cut. Wood must be cut into pieces and
stacked out of the rain for at least 6-9 months to season properly. If
no seasoned wood can be found, high-density compressed sawdust logs make
an excellent substitute. Avoid burning mill ends in woodstoves, as the
exhaust from even "untreated" mill ends has shown itself to be
tremendously corrosive to metal.

Burn The Wood
Gases

Most of the moisture content remaining in seasoned
firewood consists of wood resins. As wood heats up in the fire chamber,
these resins emit combustible gases which, when ignited in the secondary
burn chamber, can account for as much as half the heat output of the
fire. When green or wet firewood is burned, the extra water content
turns to steam and mixes with the wood gases, preventing them from
igniting and releasing their heat value. When the draft control is set
too low and the fire smolders, the wood gases won't ignite in the
resulting oxygen-starved environment, even if the firewood is properly
seasoned. When the wood gases aren't burned in the secondary burn
chamber, they escape up the chimney, taking their heat value with them
and creating heavy creosote formation.

Don't Let Creosote Build Up In The
Chimney

Creosote is a highly combustible substance which
condenses in liquid form as wood exhaust cools in the chimney, and then
solidifies as it dries. If ignited, creosote can burn for days at
temperatures exceeding 2,000 degrees, which is hot enough to destroy the
chimney and ignite surrounding combustibles. Creosote is very caustic;
if allowed to accumulate, it will significantly shorten the lifetime of
the stovepipe and chimney. A seasoned-wood fire that is given enough
oxygen for proper combustion will reduce creosote formation in two ways,
by consuming more of the wood gases while at the same time sending more
heat up the chimney to reduce flue gas cooling.

Practice Proper Chimney
Maintenance

Creosote should be removed from the chimney before
buildup in the flue exceeds 1/4" thickness. Chimneys which vent properly
operated woodstoves generally require cleaning once per year. If green
or wet wood is burned, or if the fire is allowed to smolder, the chimney
will require cleaning much more often, and should be inspected
frequently. Creosote sticks like glue, and must be removed with a
tight-fitting steel brush. Rattling tire chains down the chimney or
pulling a bag of straw through the flue won't remove creosote, and
neither will a chimney fire. Chimney fires burn away the resinous
portion of the creosote, but the sooty husk remains: if this husk isn't
removed after a chimney fire, smoke will filter through it, rapidly
re-depositing fresh liquid resin. In a very short time, the chimney will
be as bad as it was before the fire.

Follow These Woodburning
Tips

If steam bubbles and hisses out of the end grain
as the firewood heats up on the fire, the wood is wet or green, and
needs to be seasoned longer before burning.

If a wood supplier advertises his wood as "seasoned", or
claims that it has been "down" for a year or two or ten, be skeptical.
Ask if the wood has been cut into pieces and stacked out of the rain for
at least 9 months. If it hasn't, it isn't ready to burn.

Shelter the woodpile from the rain, but don't
cover it completely with plastic tarps or store it in an enclosed shed
or garage; air circulation is necessary to ensure proper
seasoning.

Never burn garbage, mill
ends, or individually wrapped compressed sawdust logs in a woodstove.
These contain chemicals which, when burned, are highly corrosive to
metal.

Unless the stove is EPA
approved, never try to make a load of fuel burn longer than 6-8 hours.
EPA approved appliances have built-in safeguards to prevent smoldering,
but many older airtight can be adjusted to smolder along for extended
periods, resulting in heavy creosote deposits.

Operate woodstoves with their draft control wide open for
20-30 minutes each time firewood is added, or until the fresh load is
totally engulfed in flames. This will send heat up the flue to help
solidify the liquid creosote deposited by the previous load, while
kindling the wood to start gasification of the resins for efficient
burning.

NEVER try to clean a chimney
by deliberately starting a chimney fire. Have the chimney professionally
cleaned and inspected at least once per year.

If a chimney fire occurs, close the draft control on the
stove completely to quench the supply of oxygen, and call the fire
department immediately. Then, make sure the chimney is thoroughly
cleaned as soon as possible.